include first 10 answers from project euler for benchmarking

Hi Robert, here is a branch containing lua scripts that solve the first 10 problems from [Project Euler](projecteuler.net). Hopefully they will work well for benchmarking luerl. 

I am calling the scripts with `timer:tc/3` for a very simple benchmark. I had to lower the limit for some of the scripts because they take a really long time to solve even with C-Lua. The originals are commented out.

Here is the output from my macbook air running `Erlang R15B03`. The time unit is microseconds.

```
➜  euler git:(euler_benchmarks) make
233168
./problem_001.lua (returned 233168.0 in 26626)
4613732 
./problem_002.lua (returned 4613732.0 in 1655)
29 
./problem_003.lua (returned 29.0 in 12110)
36863 
./problem_004.lua (returned 36863.0 in 971925)
232792560 
./problem_005.lua (returned 232792560.0 in 12651)
25164150 
./problem_006.lua (returned 25164150.0 in 2514)
617 
./problem_007.lua (returned 617.0 in 136599)
32 
./problem_008.lua (returned 32.0 in 975)
31875000 
./problem_009.lua (returned 3.1875e7 in 3329632)
277050 
./problem_010.lua (returned 277050.0 in 1145927)
```